I am reminded of the director’s commentary for Babylon 5. In the first episode where Mr Morden appears JMS starts going off about how much he looks like someone you just want to punch. For the whole time Morden’s on screen he talks about nothing but how much he wants to punch him in the face and that’s how he knew he had the right actor.

I kinda feel that’s how I know Iago was perfect for his role. Because he elicit’s such a strong reaction from everyone.